help for an allergic cat?

Have you considered he may have food allergies? Years ago, I adopted a cat from my younger sister because she'd constantly vomit with any store bought cat food fed to her. So after some thinking I tried her on an all natural cat food containing no wheat, soy, or corn. After feeding this to her, it worked. She stopped vomiting. Sometimes, certain animals can react negatively to what's in their food. I know when I fed my shepherd mix a dog food of low quality with low protein, she'd get horrible stomach aches where her stomach became painfully hard. Switching her to a more iron meat diet helped. My advice is to make your pet an appointment with the vet if possible. Second, check the ingredients in the cat food. Meat should be the first ingredient. Make sure it's not processed meat. Third, check for fleas. Your cat may have fleas, and might be allergic. Hope your kitty gets better!